Furan derivatives such as 5-methyl furfural and 5-methyl furfural alcohol as well as hydroxymethyl furfural and furfural are products of saccharide dehydration with high industrial value. The 5-hydroxy methyl furfural (5-HMF) is a multipurpose and multi functional organic molecule having wide range of application in various sectors of synthetic organic chemistry e.g. bulk chemicals, fine chemicals, pharmaceuticals, agrochemicals, polymer, and chemical intermediates etc. The structure of 5-HMF is shown below:

The process for 5-HMF synthesis is of great interest in chemical industries due to its potential for production of industrially important bio-based chemicals such as furan 2, 5-dicarboxylic acid (FDCA) which is required for production of bio-based polymer, chemicals and pharmaceuticals etc. Furans 2,5-dicarboxylic acid derived polymers have potential replacements for the petro-based terephthalic acid polymer. Thus, the huge replacement of petro based polymer by bio-based polymer provide great platform of green chemistry in the sector of polymer industry. But the key role for these replacement is synthesis of 5-HMF and therefore 5-HMF synthesis occupy nutshell position for synthesis of bio-based products.
The synthetic chemistry of 5-HMF begins with hexose sugars, glucose and fructose, more specifically from fructose via acid catalyzed cyclodehydration reaction. Since the synthetic chemistry applications for 5-HMF production is directed towards the development of acid catalysis. A number of acid catalysts like mineral acids, inorganic acids, and solid adds have been employed for this purpose. But the synthetic process for production of 5-HMF by acid catalysis suffers from many technical problems in terms of yield, selectivity, process feasibility and process economics. Due to complex chemical properties between reaction substrate, catalyst used for dehydration and reaction products separation, number of issues are raised during synthesis of 5-HMF.
Another important factor that affects 5-HMF synthesis is the type of catalyst used for dehydration reaction. Various types of organic, inorganic and mineral acids have been employed as in situ catalysts for 5-HMF synthesis. But most of these processes suffer from handling problems due to corrosive nature of mineral acids as well as difficult catalyst separation protocols from reaction mixture with subsequent recycling of the catalyst.
Therefore heterogeneous acid catalysis as well as various solid acid catalysts such as zeolites, silica, and amberlyst resins have been explored and investigated as a possible alternative. Ken-ichi Shimizu and co-workers reported use of heteropoly acid, zeolites, and acidic resin (Catalysis Communications, 2009, 10, 1849-1853) with DMSO as solvent. Though the use of heterogeneous catalysis resulted in higher yield, high boiling point of solvent rendered separation of the product difficult.
Yugen zhang report (ChemSusChem, 2011, 12, 1745-1748) disclosed the synthesis of 5-HMF in isopropyl alcohol with aqueous HCl as a catalyst. However, the use of halogenated corrosive HCl as a catalyst in aqueous condition resulted in product separation problem as well as recovery of catalyst with difficulty in handling during large scale production.
US2007757461 discloses use of mineral acid, zeolites, silica-, silica-alumina, and titania-based supports functionalized by acid groups, cation exchange resin, Lewis acid, heteropolyacid, in biphasic reactor, having aqueous and organic phase of 1-butanol, DCM, MIBK, 2-butanol, and mixtures thereof. However, the invention also employs modifier such as DMSO, DMF, N-methyl pyrrolidinone (NMP), which are difficult to separate and non eco-friendly.
Similarly patent documents WO2009/076627, US2009/0156841, U.S. Pat. No. 7,579,489, EP2233476, and Lve et. al (ChemSusChem, 2012, 5, 1737-1742) disclose the use of a heterogeneous catalyst, amberlyst-35 resin, in high boiling solvents like DMF, N-methylpyrrolidinone (NMP) with yield figure less than 80%. The solvents used are non green and require high energy to separate them from reaction mass.
Typically aqueous biphasic solvents and ionic liquids are used for the synthesis of 5-HMF in presence of acid catalyst. However, due to higher solubility of 5-HMF in water, procedures become complicated and require large amounts of organic solvents for extraction. This leads to substantial increase in the process cost and unit operation for the bulk production of 5-HMF. This necessitates the optimization of solvent and catalytic systems that would be cost effective as well as provide ease of process operation.
WO2011124639 recites claims to the use of mineral and Lewis acid catalyst such as aqueous HCl, AlCl3 respectively by using salt, NaCl, LiCl, LiBr, LiNO3, KCl, KBr, KNO3, FeCl3, etc. in biphasic organic solvent, wherein the biphasic organic solvent consisted of mixture of water and methyl isobutyl ketone (MIBK). However, the disclosed process of the invention resulted in low yield (52%) and selectivity (less than 65%). The process also employs halogenated catalyst and salts which cause corrosion problems as well as environmental hazards.
Microwave assisted reaction for synthesis of 5-HMF has gained significance as it leads to reduction in reaction time, increases selectivity and also results in reduction of energy consumptions. Thomas S. Hansen and co-workers (Carbohydrate Research, 2009, 344, 2568-2572) reported microwave assisted synthesis of 5-HMF by using Aq. HCl catalyst at 200° C. temp with only 52% HMF yield. Xinhua Qi, and co-workers (Ind. Eng. Chem. Res. 2008, 47, 9234-9239) reported HMF synthesis by employing strong acidic cation-exchange resin catalyst and a mixed organic solvent system comprising acetone and DMSO in ratio of 70:30 w/w under microwave heating condition. The reaction resulted in 80% yield with a reaction time period of 10-30 min.
Sudipta De and co-workers (Green Chem, 2011, 13, 2859) report microwave assisted synthesis of 5-HMF by using Lewis acid catalyst AlCl3 with 21.4-60.6% yields in solvent DMSO and biphasic system, water—MIBK. Xinhua Qi and co-workers (Green Chem., 2008, 10, 799-805) employed microwave assisted heating for HMF synthesis in acetone-water mixtures in the presence of a cation exchange resin catalyst with yields of 5-HMF as high as 73.4%, with 94% conversion rate at 150° C. Sakita Dutta and co-workers (Applied Catalysis A vol. 409-410, 133-139), carried out microwave assisted 5-HMF synthesis by using mesoporous TiO2 nanoparticals in solvents DMSO and NMP.
WO2012/015616 A1 claims for microwave assisted synthesis of 5-HMF by using catalyst amberlyst and H2SO4 in 5-30 min reaction time with 0-69.47% yield by using DMSO solvent. These methods of the microwave assisted synthesis for 5-HMF also reflect earlier predicaments of lower yield, selectivity, use of non-green solvent systems and higher cost economics that affect scaling up of the processes adversely.
WO2014180979 discloses a process for the synthesis of 5-hydroxymethyl furfural (HMF) from saccharides. In particular it discloses a process for the dehydration of monosaccharides having 6 carbon atoms (hexoses), disaccharides, oligosaccharides and polysaccharides deriving therefrom to yield highly pure 5-hydroxymethyl furfural (HMF) in high yield.
The methods of prior art disclose the use of various catalyst and solvent systems for synthesis of 5-HMF through microwave assisted as well as conventional means. Evidently, these methods are associated with issues pertaining to higher cost economics, reaction feasibility, longer reaction time, catalysts and product separation, low catalyst activity, low selectivity & yield, and use of non-green solvents that pose environmental hazards.
Accordingly, there has been a need in the prior art for a process for synthesis of 5-HMF, wherein the process results in higher selectivity and yield; has a higher conversion rate with enhanced catalytic stability, has ease of product separation and most importantly has the advantage of recycling the catalyst with 100% recovery.